1. Field of the Invention
The present invention relates generally to an improved method and apparatus for determining the pressure of a fluid. More specifically, the apparatus includes a deformable rubber pad which is compressed non-uniformly in response to fluid pressure to reduce the overall resistance of an electrical system in inverse proportion to the fluid pressure.
2. The Prior Art
Various types of switches and gauges have been used in the prior art to measure the pressure of fluids. For example, automobiles include either a so-called idiot-light or a gauge to provide a visual indication of oil pressure. The normal pressure switch used in an idiot-light circuit includes a spring-biased contact element responsive to oil pressure to close an electrical circuit when oil pressure is low, this type of switch being relatively simple in both construction and operation.
This contrasts rather sharply with the pressure switches that are required for gauge indicator systems, since a variable oil pressure measurement is constantly provided. The most common pressure switch used in the prior art for this type of system includes a plunger which moves a pivotal arm in response to oil pressure. The pivotal arm is in contact with a resistor element which generally takes the form of a wire wound around a non-conductive supporting element. At low oil pressures, the arm will be positioned at one extreme end of the resistor element to provide a relatively high resistance in the system. This, quite obviously, reduces electrical current flow to the readout gauge. At higher oil pressures, the plunger moves the pivotal arm along the resistor element to reduce the overall effective resistance to thereby increase electrical current flow through the system, so that the readout gauge will reflect the increased oil pressure.
Although the prior art pressure switches for gauge-type systems provide a relatively high degree of accuracy, they exhibit several shortcomings which are eliminated by the present invention. Specifically, the prior art devices exhibit a relatively high failure rate, apparently as a result of automotive engine vibration. More importantly, though, the prior art devices are relatively expensive due to the number of parts involved and the required assembly.
The present invention overcomes these problems by a device which includes a small number of moving parts that are relatively inexpensive and easily assembled.